We have a similar mattress to yours except that our topper doesn't come off. I dried as much of the wet area with a dry absorbent cloth/towel then with a damp cloth went over the area then dried it again as much as possible. From the supermarket I bought a product called Protect-A-Bed - Odour Eliminator Fabric Treatment. It is in a pink box with pictures of people on the front. It is suppose to get rid of the smell of urine, vomit etc... You spray it on the area, rub in then let it dry. We have an overhead fan so that helped with the drying process. I can't smell anything on ours or DD mattress (she has had a wee accident and also vomitted)
GL